William d



No. 6l4,946. Patented Nov. 29, I898. W. D. GHARKY.

TELEPHONIC MICROPHONE.

(Application filed Dec. 20, 1897.)

(No Model.)

INVE/YTDF? THE NOFUHS PEYERS co. wofouma, WASHINGTON. n. c.

UNITED STATES PATENT OFFICE.-

i-viLt-irxn D. GHARKY, or PHILADELPHIA, PENNSYLVANIA, ASSIGNOR To GEORGE F. PAYNE, or SAME PLACE.

l'ELEPHONI C MICROFHONE;

SPECIFICATION forming part of Letters Patent Lib. 614,946, dated Ll'ovemloer 2 9, 189 Application filed Decembei 20,1897. Serial No; 662,510. (No nio'delz) To all whom it may concern:

Be it known that 1, WILLIAM D. GHARKY, a citizen of the United States of America, residing in the city and county of Philadelphia, in the State of Pennsylvania, have invented a certain new and useful Improvement in with the. approved form of microphone in which granulated conducting material, preferably carbon granules, is used as the variable resisitance, the density of the primary battery-current, which it is practical to use on the primary circuit, including the microphone, has been limited by the heating effect of the current upon the microphone, such heating effect as the density of the current is increased producing first a disturbing sound and on further increase actually destroying the microphone as a practical device. The limitation on the density of the primary battery-current imposed by the above considerations is a limitation also on the power of the transmitter as awhole, limiting, of course, the induced current in the secondary circuit. I have discovered that the density of the primary current may be materially increased, with the consequent increase in the power of the transmitter, by combining with the microphone a thermopile, junctions ofthe elements of which are arranged in such relation to the microphone as to be heated thereby and'in which the effect of the current is to absorb or to convey away the heat fromtheseheated junctions, preferably availing myself of the well-known Peltier effect produced by passing an electric current through a thermopile, although the current directly generated by heating the contacts of the dissimilar materials in the pile is also availed of to a certain extent.

The nature of my invention and its mode of application in different ways will bestbe understood as described in connection with the drawings in which it is illustrated, and in which- Figure l is a diagrammatic illustration of a thermopile and the mannerin which a current is generated therein by heating certain of the unions formed between its elements. Fig. 2 is a diagrammatic illustration of a thermopile coupled in circuit with the battery and arranged to illustrate in a convenient way the Peltier effect. Fig. 3 is a view illustrating a microphone constructed in accordance with my invention and embodying a mode of construction which in principle would produce the maximum refrigerating effect upon the heated portions of the microphone. Fig. 4 is a view illustrating another mode of applying my invention in use, which by reason of its simplicity of construction, as Well as its practically successful operation, will probably be found to be the best commercial embodiment of my invention; and Figs. 5 to 18, inclusive, are views illustrating various modifications in details of construction, all embodying the fundamental features of my invention, but which will best be explained more in detail hereinafter.

D in Fig. 1 indicates a thermopile made up of, relatively speaking, positive and negative elements, the positive elements being indicated at d and the relatively negative elements at (1 If now the alternate unions of the elements composing the pilesas, for instance, d d d -be heated, as by candles J J, &c., while the remaining unions, as d d, are cooled or left at a lower temperature, a thermo-electric current is generated, and if the ends of the pile be c0nnected, as by a circuit-wire F, the current will be indicated by a galvanometer K, placed in the circuit, the current flowing in the direction from the positive to the relatively negative elements of the pile at the heated junctions, and the passage of the current from the negative to the posi-- tive elements of the pile at the cooler j unctions (2 has, according to the well-known Peltier effect, the result of heating these junctions, the result being,'in effect, to transfer the heat directly communicated to the j unction d to the outer junctions, so to speak, d

to a much greater extent and much more rapidly than would be the case if reliance was placed entirely in the heat-conductivity of the materials comprising the pile.

In Fig. 2 of the drawings I have shown a thermopile D, made up of relatively positive elements cl and negative elements 61 so arranged that the current generated in a battery G, connected with the pile, as by a circuit-wire F, will first pass through a junction (l passing from the positive to the negative elements of the pile, and then through a junction (Z at which the current passes from a negative to a positive element of the pile. The effect of this, according to Peltiers discovery, is to cool the junction (indicated at d) at which the current passes from the positive to the negative element and to heat the junction (indicated at (F) Where the current passes from the negative to the positive element of the pile, an effect which can be readily detected by bringing into contact with the junctions alternately a test-couple with a galvanometer in its circuit, as indicated at L, the test-couple consisting of two bars of metal of dissimilar thermo-electrical value forming a union at one end, while their other ends are connected in circuit with a galvanometer. It will be obvious that with a testing device of this kind the degree of heat applied to the union of the two bars will be satisfactorily shown on the galvanometer, the current generated being proportional to the heat applied to the junction of the test-bars. The effect of the current passing through the junction (1 in Fig. 2 being to cool down this junction, it is obvious that if the junction be exposed simultaneously with the passage of the current to an extraneous heating effect the heat imparted to it will be absorbed or carried away to reappear again in the junction d at which the current passes from the negative to the positive elements of the pile.

My invention, broadly speaking, consists in availing myself of the above-described properties of the thermopile either jointly or sepa rately, which I do by incorporating a thermopile with the telephonic microphone in such a way that the junction (1 at which the current passes from the positive to the negative elements, will thus form the electrodes or walls of the microphone-chamber or else be so incorporated with the electrodes or walls of the chamber as to be readily heated thereby, while the other unions (1 of the pile are so arranged as to be at some distance from the microphone, so that the heat imparted to them by the passage of the current from the negative to the positive elements of the pile will not affect the microphone, the said unions being preferably situated at apoint or points where their temperature will be constantly lowered, as by exposure to the air. Thus in Fig 3 I have shown a telephonic microphone ha ,ng positive and negative electrode faces B of carbon, between which is situated dea. bonaceous material, (indicated cated at (1 at 0,) and at the back of the positive-electrode face A, and forming, as it were, a part of the same electrode-button,I have shown a thermopile D, made up of coupled elements, of which those indicated at cl are, thermo-electrically speaking, positive with regard to those indi- The junctions d of the elements of the pile at which the current passes from positive to negative elements are placed in close juxtaposition with the back of the positive-electrode face A, while the junctions (1 at which the current passes from the negative to the positive metals, are placed as far as practicable from the face of the electrode. E in this diagram indicates the diaphragm of a transmitter; F, a circuit-wire by which the primary circuit of the battery G is conveyed through the microphone. G H indicate the coil of the converter, and I insulating material interposed between the junctions d of the thermopile and the rear face of the positive electrode, the circuit being in this construction through the thermopile, thence through the upper positive element cl to the electrodeface A, thence through the granular earbonaceous material C and negative-electrode face B to the diaphragm, which is in electrical connection with the battery. In this construction it will be observed that the insulating material I should be of such character as to convey heat with reasonable facility while completely insulating the junctions of the thermopile and .the electrode-faces electrically. The result of this construction, for the reasons already explained, will be that the thermopile will absorb the heat of the electrode-face A, transposing it, so to speak, to the outer junction d of the pile and with the effect of cooling the microphone proper and rendering it practicable to use a current of much greater density than has heretofore been the case.

In Fig. 4 of the drawings Ihave shown anothermode of applying my invention in which the microphone is incorporated, so to speak, in the thermopile. In this construction the positive electrode A is backed by a thermoelectrically-positive material (1 and the negative electrode B is backed with a thermoelectrieally-negative material (1, and it is to be understood that the elements of the thermopile should be made as dissimilar as practicable. Thus in practice I have used for the thermo-electrically-positive material bismuth and for the thermo-electrically-negative material an alloy of antimony and zincin the proportion of about two parts of antimony to one of zinc by weight. The thermo-electrical value of carbon is practically midway between that of the positive and negative elements referred to and may be disregarded, so that in the construction shown the current can be considered as passing directly from the positive bismuth to the negative alloy or from the positive bismuth to the relatively-negative carbon and from the relatively-positive carbon to the negative alloy. From whichever point of view the pile incorporating the microphone is considered it will be obvious that the passage of a current through the microphone so constructed will tend to cool it down or to remove heat due to the Joule effect. It will be obvious that apart from practical conditions affecting the durability of the microphone the positive and negative metals can themselves be used as the electrodes of the microphone without the presence of carbon faces, such a construction being indicated in Fig. 5, and also that my invention is applicable to microphones in which granular conducting material is not used, as shown, for instance, in Fig. 6, where the contacting electrodes faced with carbon are shown with the carbon faces in direct contact with each other. So, also, in Fig. 7a form of microphone is shown in which the thermo-electrically-negative material d faced with carbon 13, is in contact with a positive terminal or electrode (1.

As shown in Figs. 3 and 4, the current passed through the thermopile is that of the battery of the primary telephone-circuitthe same current which passes through the microphone. Whilethis is convenient in practice, it is not in any wise essential, and in Fig.

8 I have illustrated a construction in which.

a thermopile arranged in connection with the positive -electrode face A, substantially as shown in Fig. 2, is entirely insulated electrically from the said electrode-face andprovided with an independent battery G and circuit-wire F, the current from the said battery G passing through the thermopile, but not through the microphone, which is provided with its own battery G. It is obvious that the effect of this construction in the cooling of the microphone will be the same as in the constructions already described.

In Fig. 9 I have shown a construction in which the physical and electrical connection between the positive-electrode face A and the thermopile D is like that shown in Fig.2, but in which an additional battery G2 is placed in a portion F of the circuit, between which portion and the portion F of the circuit connection is made with a negative-electrode face B. In this constructiona current of the combined density due to the united action of the batteries G and G2 will flow through the thermopile, while the amount of current flowing through the microphone will be of only the density due to the difference in the potential of the batteries G and G Such a construction as this has certain ad-.

vantages, owing to the fact. that the even limit of the cooling effect of the current upon the junctions d of the thermopile is proportioned to the density of the current.

In Fig. 10 I have illustrated a construction in which no current is passed through the thermopile D except that generated therein by the heat of its junctions d by contact with the electrode-face, the outer elements of the pile being simply connected by circuit-wire.

In Fig. 11 I have diagrammatically shown a construction in which junction 01 thermoelectric couples united at both ends are placed in contact with one of the electrodefaces. This in effect is the same as the construction shown in Fig. 10, except that each t-hermo-electric couple in this case forms a separate and independent pile, any desired number of which may be used.

In Fig. 12 I have shown a similar arrangement to that shown in Fig. 11, except that I have indicated the thermo-electric couples as in themselves constituting one of the electrodes of the microphone, it being obvious that the passage of the primary transmittercircuit through the thermo-electric couples will not interfere with the thermo-electric current generated in the couples.

In Fig. 13 I have illustrated a constructio in which instead of arranging the thermoelectric pile in such manner as to serve as or receive heat from the electrode-face of the microphones I arrange it so as to practically form the whole or a part of the walls of the chamber in which the electrodes are placed, in which position it will absorb heat from the granular carbon in contact with and serve, as before, to prevent the overheating of the microphone. Obviously the outer wall of the chamber has a smaller contact with the granular material than do the electrodes which form its end walls, and for this reason the device of Fig. 13 does not present the same advantages in use, although it may be desirable in certain cases to use it either alone or in connection with electrodes, which are also combined with thermo-electric iles.

p I have shown and described the electrodes backed by or incorporated in the elements of the thermopile as faced with carbon plates such as are usually employed to face microphone-electrodes, and it will be recognized by those skilled in the art that a facing of hard carbon or equivalent material like it in not being easily oxidizable is peculiarly advantageous in my new construction.

Having now described my invention, what I claim as new, and desire to secure by Letters Patent, is-

1. A telephone-microphone having a thermopile arranged in connection therewith with its junction or junctions through which an electric current passes from positive to negative elements arranged to be heated by the heat generated in the microphone and its junction or junctions through which the current passes from negative to positive elements arranged at a distance from the heatgenerating portion of the microphone and so that the heat generated in the microphone is conveyed away by the action of the current in the pile.

2. A telephone-microphone having a thermopile made up of materials having a marked difference in their thermo-electric order arranged in connection therewith with its junction or junctions through which an IIO ii I 614,946

electric current passes from positive to negative elements arranged to be heated by the heat generated in the microphone and its junction or junctions through which the current passes from negative to positive elements arranged at a distance from the heatgenerating portion of the microphone and so that the heat generated in the microphone is conveyed away by the action of the current in the pile.

3. A telephone-microphone having granular conducting material inclosed in walls and having a thermopile arranged in connection with a wall or walls of the microphone with its junction or junctions through which an electric current passes from positive to negative elements arranged to be heated by the heat generated in the microphone and its junction or junctions through which the current passes from negative to positive elements arranged at a distance from the heatgenerating portion of the microphone and so that the heat generated in the microphone is conveyed away by the action of the current in the pile.

4. A telepholie-microphone having a thermopile arranged in connection therewith with its junction or junctions through which an electric current passes from positive to negative elements arranged to be heated by the heat generated in the microphone and its junction or junctions through which the current passes from negative to positive elements arranged at a distance from the heatgenerating portion of the microphone and so that the heat generated in the microphone is conveyed away by the action of the current in the pile, and a batteryand circuit connections therefrom to the pile arranged as specified to send a current through the pile in the direction indicated.

5. Atelephonic microphonehavin g the elements of a thermopile incorporated in its electrodes as described and so that the electric current passing through the microphone will simultaneously pass through a junction of the thermopile from a positive to a negative element thereof, whereby the heat generated by the resistance of the microphone is conveyed away by the action of the current in the pile.

6. A telephonic microphone having electrodes faced with material not readily oxidizable and backed by materials forming a thermopile arranged as specified and whereby the heat generated in the microphone is absorbed or conveyed away by the action of the current in the pile.

7. A telephonic microphone having granular conducting material held between electrodes faced with material not readily oxidizable and backed by materials forming a thermopile arranged as specified and whereby the heat generated in the microphone is absorbed or conveyed away by the action of the current in the pile.

S. A telephonic microphone having one or more electrode-buttons constructed as specified to form a thermopile in electrical circuit with the electrodes and having the con tacting elements of the pile in such relation that the current through the electrodes will pass through the junctions of the pile which are in close relation to the faces of the electrodes from the positive to the negative elements.

9. A telephonic microphone having a positive electrode of high thermo-electric value and a negative electrode of relatively low thermoelectric value.

7M. 1). GHARKY.

\Vitnesses:

CHAS. F. MYEns, D. STEWART. 

